Editing Protein engineering (section)

====Mutator strains====
Mutator strains are bacterial cell lines which are deficient in one or more DNA repair mechanisms. An example of a mutator strand is the E. coli XL1-RED.<ref name=PoluriBook/>{{page needed|date=May 2017}} This subordinate strain of E. coli is deficient in the MutS, MutD, MutT DNA repair pathways. Use of mutator strains is useful at introducing many types of mutation; however, these strains show progressive sickness of culture because of the accumulation of mutations in the strains own genome.<ref name=PoluriBook/>{{page needed|date=May 2017}}